1. Field of Invention
This invention relates to hybrid vee-hull planing boats incorporating wing-in-ground effect chines, sponsons, or external appendages.
2. Description of Prior Art
Conventional vee-hull planing boats are designed to cut through waves without pounding or slamming but sacrifice speed and transverse stability for comfort. The fineness of the forward vee-section of the hull determines the smoothness of the ride. A narrow vee-section sinks deeper into the water to support the same amount of weight as a wider flatter vee-section. Narrow vee-hulls inherently have increased wetted surface, which ultimately results in increased drag in the water. To balance this effect conventional vee-hulls have a narrow vee-section forward transitioning into a wide flat vee-section aft. Flattening the vee-shape makes conventional vee-hulls more transversely stable and increases attainable high-end speed of the vessel. A narrow forward section helps soften the impact of waves providing a smoother ride when compared to vessels with fuller or blunt forward hull sections.
Conventional planing vee-hulls may have chines. The motion of conventional vee-hulls tends to be transversely tender when planing, as previously stated. A person walking from one side of the boat to the other side causes the vessel to lean from side to side as well. To remedy this the outboard chines are frequently designed into the hull. The chines are narrow, run parallel to the waterline, and are above the centerline vee-section of the hull.
Weight distribution and interior accommodation are challenges in any vessel. The center of gravity of the boat must be located directly over the center of buoyancy of the hull at its designed waterline. If the two centers are not located in the same plane, the boat will trim and list until they are. If there is more weight to one side then the boat will list, lean to that side. If there is more weight aft the boat will trim aft, sit lower in the water by the stern.
To achieve balance, conventional hulls have engines forward from the stern of the vessel. This encroaches on interior space and compromises the comfort of the vessel due to noise and heat from the engine. Also, lines must be run to the engine for cooling, intake air, and exhaust. Exhaust lines become quite hot requiring bulky insulation. An insulated housing is typically fashioned around the engine itself to deaden engine noise and contain heat. The housing significantly reduces the available space for personal accommodation. This type of engine mounting also requires a propeller shaft to run from the engine aft, normally under the boat or inside the hull to a stern drive propeller. If the shaft is under the boat, it is subject to damage should the boat run aground or hit debris in the water. The shaft configuration below the hull produces significant drag lowering the speed of the vessel and increasing operating cost. Both configurations require bearing supports along the shaft length to ensure it turns freely and does not vibrate. Propeller shafts turn at high speeds so vibrations in propeller shafts and shaft alignment with the engine are critical concerns.
Stern drive boats have engines directly coupled to the stern drive through the transom. This keeps the machinery in one location. Engines still encroach on deck space, but noise concerns are less since aft cockpits are normally open spaces and intake air is easily obtainable. To counter the concentration of weight aft, fuel and water tanks are located forward. The distribution of weight must be maintained about the vessel's center of buoyancy or the vessel will trim with her bow up or down. Close inspection of stern drive boats show that they trim aft and sit lower in the water by the stern. If the boat has her bow up, the fine forward entry of the vee-hull is not in the water so the boat will pound in a seaway and it is much more difficult for the driver to see. If the bow trims down then the boat will have a tendency to bury her bow in a seaway. This is critical since full fuel tanks represent significant weight. As the fuel tanks empty the center of weight moves, strongly impacting vessel characteristics and safety. Trim tabs are added to compensate for this design flaw. Trim tabs are attached to a vessel's transom and can be angled to deflect water. When a boat is traveling, trim tabs are adjusted as required to compensate for changing weight distribution.
As boating has matured there are many more boaters on the water and the potential for accidents has dramatically increased. Several accidents have occurred in planing boats when the operator applied full throttle from a dead stop or slow speed. Thrust applied by the propellers is below the hull and induces a strong moment that causes a boat's bow to rise dramatically for a short period of time. When the stern of a boat digs down into the water the bow rises and the driver is temporarily unable to see over the bow. Ski boats and speedboats racing from a start are prime examples of this kind of hazard but the phenomenon is common to all planing boats.
Objects and Advantages
The primary embodiment of this patent is a planing boat hull having a conventional vee-hull forward with enhanced outboard chines. The outboard chines may appear to be conventional when the boat sits at rest in the water, or is not planing. The chines typically originate at the bow above the waterline transitioning as they go aft, ultimately extending below the center vee-hull. The outboard chines also become wider as the chines transition aft. When planing, the proposed boat rides on the outboard chines, lifting the center vee-hull out of the water thereby reducing wetted surface and drag, while enhancing transverse stability. Air trapped between the two chines and the water creates a wing-in-ground effect of buffered air adding lifting forces on the hull and further reducing drag at planing speeds. This lifting force on the hull is augmented by water, which impacts the curved/cupped after sections of the vee-bottom of the hull and is deflected down. A ram air effect is also induced by the changing width of the outboard chines as they transition aft. The distance between the chines is greater in the bow creating a funnel for air. A large volume of air is trapped under the bow of the boat as it planes. This volume of air must remain constant as it goes under the boat. The result of the narrowing gap between the chines, as the chines transition aft, is to create a buffered layer of accelerated air. The buffered layer of accelerated air acts to increase the lift on the boat reducing the hull drag in the water. The present invention has a forward center vee-section of the hull to ensure the boat will not slam or pound in a seaway and additional lift generated by buffered air under the hull ensures a measurably smoother and faster ride. Existing vee-hulls have a higher wetted surface, while planing, creating more drag and providing less lift at speed. Conventional vee-hulls are also notably less transversely stable, and have a rougher ride. In the preferred embodiment of the proposed hybrid boat the centerline vee-hull can become shallower as it transitions aft to further enhance the wing-in-ground effect. An example of this is shown in the 32-foot hull referenced in FIG. 1 through FIG. 7. Another example of the embodiment of this hybrid hull is shown in a 55-foot boat referenced in FIG. 8 through FIG. 10. The 55-foot boat shows engines and water jets installed in the outboard chines. The 55-foot boat does not have the centerline vee-hull elevated as it transitions aft from amidships but the 32-foot boat does.
Fuel and water tanks can be fitted below the deck centered over the vessels design center of buoyancy. Tanks placed in this location will not effect the trim of the vessel regardless of how full or empty the tanks are. The added advantage is that no interior space need be compromised to achieve this placement and safety is further enhanced over conventional vessels. A balance must be made between required buoyancy, outboard chine draft, and outboard chine width. Adjusting these variables allows for fuel and water tanks to be placed over the center of buoyancy. The 32-foot boat design example embodying this patent has 2,200 pounds of fuel when fully loaded. The total displacement of the vessel is 7,500 pounds when fully loaded. Fuel weight represents 30% of the vessel weight when fully loaded. If the fuel were not located over the center of buoyancy the change in fore and aft trim of the boat with fuel consumption would be dramatic. In the 32-foot boat design the center of buoyancy of the hull moves aft 5 inches from full load to light ship draft. This requires the center of the fuel in the fuel tanks to move aft when fuel is consumed. Since the outboard chines get deeper and wider as the chines transition aft a single fuel tank spanning the width of the vessel is easily designed with the proper characteristics.
The outboard chines of the proposed hull can be designed with enough width and depth for the engines and drive systems to be mounted inside them. Interior accommodation need not be encroached upon with the proposed design. The proposed design is ideal for placing water jets in the outboard chines since water jets require a flat surface for water intake. Whether stern drives or water jets are used the lowered aft chines provide buoyancy in the stem where it is needed to offset the machinery weight. Trim tabs are not required to ensure proper trim of the proposed design over a range of drafts and speeds. This enhances the safety and efficiency of the proposed boat hull.
In smaller boats where outboard motors are used the motors can be set inboard of the chines of the proposed hull. The propellers can be safely above the bottom of the boat and have unobstructed water flow. The propellers are protected in a grounding situation since they are above the outboard chines. Also, the propellers always have clean unobstructed water flow, as mentioned, resulting in enhanced performance over hulls which have a small center section of the hull cut away for the propeller to be protected in a grounding situation.
Inherent in this proposed design is the ability to maintain level pitch under acceleration, which dramatically improves safety. Conventional planing hulls initially assume a “bow up” position when the vessel transitions between displacement speed and planing speed. High thrust applied by the propeller deep in the water and far aft creates a moment, which causes conventional boats to raise their bow, usually blocking the sight of the helmsman. The proposed design eliminates this as the energy provided is being countered by increased water velocity to the lower chines at a similar elevation and the forward portion of the vee-hull acts like a cantilevered beam keeping the bow down.
The hull can be optimized for speed and comfort by changing the centerline vee and the outboard chines. The centerline vee section of the hull acts as a shock absorber deflecting waves. The wider the centerline vee section the more buoyancy it provides resulting in a stiffer bumpier ride. Maximizing the depth of the centerline vee also reduces speed but makes the ride smoother. A step can be added to the centerline vee to introduce turbulent flow in the water behind the step enhancing the water and air mixture trapped between the two outboard chines. Adding a step only helps at higher speeds provided the centerline vee is immersed forward of the step. The outboard chines can be made deeper providing a more cushioned but slower ride. The can also be made shallower providing a faster but bouncier ride. The width of the outboard chines is also critical in producing a wake at speed.
The wake produced by the outboard chines and the centerline vee can be optimized to cancel each other at speed ranges just as a bulbous bow does on a ship. Preliminary test shows that it is possible to reduce the wake of the hull configuration by adjusting the after sections of the centerline vee along with the width and depth of the outboard chines. The inboard wake produced by the outboard chines can be canceled by the centerline vee or by each other. The result is to produce a faster more efficient hull over a given range of speeds.
All of the properties of the hybrid vee-hull combine to make it faster and significantly more comfortable boat when compared to existing designs. At low speeds this hull does have increased drag over a flat-bottomed boat but also has much greater transverse stability. At high speeds the increased transverse stability keeps the boat from healing during sharp turns and ensures proper tracking of the hull.
In summary, the primary objects and advantages of the hybrid vee-hull in the present invention are:                a) A centerline vee-section forward to cut through seas reducing hull slamming loads and providing directional stability coupled with outboard chines.        b) Outboard chines extending below the centerline vee-section aft wide enough to provide lift at speed.        c) The outboard chines may be narrower forward increasing in width as the chines transition aft. This creates a funnel or ram air effect adding to lift on the boat.        d) Water bouncing off the cupped after sections of the centerline vee-hull is pushed back down which creates additional lift on the hull.        e) The outboard chines provide additional transverse stability over conventional hulls.        f) Air trapped between the outboard chines and the water creates a wing-in-ground effect where buffered air raises the boat out of the water thereby reducing drag.        g) Design improves weight distribution by adding buoyancy aft where machinery weights are ideally concentrated.        h) Design produces improved pitch stability at all ranges of acceleration. Thrust from the propellers is above the bottom of the outboard chines so the induced pitching moment when accelerating is minimized due to the shorter moment arm distance to the water surface and the large inherent buoyant force aft.        i) Design significantly improves the safety of the vessel as a result of improved stability and visibility by the helmsman in all conditions.        j) Design can house water jets, and in larger vessels primary engines. Both reduce the intrusion of propulsion systems into the personal accommodation spaces and increase the versatility of interior design space.        k) Design results in an extremely shallow hull draft utilizing water jets housed in the outboard chines. This hull can travel over shallow shoals conventional boats would not manage.        l) Design protects propellers during grounding.        m) Design can have increased beam for the same displacement when compared to a typical vee-hull because the outboard chines support the vessel. The added beam allows for increased interior and aft deck space. It also enhances the wing-in-ground effect by providing a larger surface providing lift.        n) Design provides enhanced tracking during turns and reduces healing as a result of the outboard chines.        o) Design can be optimized to produce less wake at speed through “wake canceling” providing less drag over conventional hulls.        
Further objects and advantages achieved with the advent of this invention will become apparent from a consideration of the drawings and ensuing description.